Cut Square Used As Postage On Envelope

Just found this interesting usage example. It's pretty beat up, is there any value in this, of merely curiosity ?

First I am announcing that I am completely ignoring any condition issues on the item shown.

This is an illegal use of the cut square and it can be found one of three ways. As shown where it appears to have been accepted as proper postage with a nice tying cancellation. Used with a tying cancellation but rejected as postage with the same amount collected as postage due. Noted at time of acceptance as being invalid, not postmarked but otherwise noted as not valid (zero by it, "x" out, "not valid" and similar marks or phrases).

All version have interest with collectors. Of the three, yours likely carries the least interest (read price) of the three but still more than a normal usage.

That all said, yours has the added interest due to the placement of the cut square.

Edited for missing one of these, " " " marks.